alcoon61 Posted September 21, 2010 Share Posted September 21, 2010 Well not sure what I have gotten into here. I have gone from a freightliner mechanic to a Mack mechanic. My air dryer is blowing off every minute and 40 seconds or so. No noticeable leaks. Replaced the governor today. Nothing changed. After a lot of reading I am suspecting a problem with the unloader valve. I think this is a wabco compressor but not sure. How hard is it to repair the unloader in these? Cant find much literature on these like bendix has. I am getting a lot of water from the air tanks daily when I drain them. I checked the power to the dryer and have 14 volts. I omhed the two prongs on the dryer and could not get a reading at all. Does this mean the heater element is bad? Mack does a good job of painting over id labels and etc to make sure you come to mack for parts. If anybody has a source to look up by vin please send me the part numbers and make for the dryer and compressor. The last six of the vin is 014310.I know I sure would like to put my foot in the seat of the pants of the engineer at mack that dreamed up putting the dryer directly under the bunk on the frame a foot or so below my pillow. "Nothing but genuius" Sounds like a rifle when it goes off.Any other suggestion or help with chasing down a solution would be greatly appreciated.Thanks,Andy Quote Link to comment Share on other sites More sharing options...
e9500v8 Posted September 21, 2010 Share Posted September 21, 2010 Well not sure what I have gotten into here. I have gone from a freightliner mechanic to a Mack mechanic. My air dryer is blowing off every minute and 40 seconds or so. No noticeable leaks. Replaced the governor today. Nothing changed. After a lot of reading I am suspecting a problem with the unloader valve. I think this is a wabco compressor but not sure. How hard is it to repair the unloader in these? Cant find much literature on these like bendix has. I am getting a lot of water from the air tanks daily when I drain them. I checked the power to the dryer and have 14 volts. I omhed the two prongs on the dryer and could not get a reading at all. Does this mean the heater element is bad? Mack does a good job of painting over id labels and etc to make sure you come to mack for parts. If anybody has a source to look up by vin please send me the part numbers and make for the dryer and compressor. The last six of the vin is 014310.I know I sure would like to put my foot in the seat of the pants of the engineer at mack that dreamed up putting the dryer directly under the bunk on the frame a foot or so below my pillow. "Nothing but genuius" Sounds like a rifle when it goes off.Any other suggestion or help with chasing down a solution would be greatly appreciated.Thanks,Andy Quote Link to comment Share on other sites More sharing options...
Mackpro Posted September 21, 2010 Share Posted September 21, 2010 You do have a Wabco compresssor and a Bendix AD9 air dryer on your truck. The Wabco compressors did have problems with their valves getting gummed up with carbon/sludge but this usually caused the compressor not to build up air or build up slowly. We had alot of Pilgiram Pride chicken trucks have this problem and had to replace the compressor head with a new updated head. Although I never remember it affecting the air dryer operation. Quote Link to comment Share on other sites More sharing options...
e9500v8 Posted September 21, 2010 Share Posted September 21, 2010 The little line from air govener to air dryer could be clogged I have ran into that before just unhook both ends and blow through it with shop air see what comes out I bet that is your problem Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted September 21, 2010 Share Posted September 21, 2010 when ever this happend I had a the air/water separater was clogged or the filter was old. Mine did this every 40 sec and after I replaced it (5 years ago) it acts normal. I really only notice it only kicking off after the gov kicks out. Quote Link to comment Share on other sites More sharing options...
CML Service Posted September 23, 2010 Share Posted September 23, 2010 Had this problem on IH's with DT's and AD-9. Ussually heat build up in drier hardens orings and causes pressure to bleed of restating compressor and cycling drier over and over. Check Bendix website for updates and part kit numbers. Chuck Quote Link to comment Share on other sites More sharing options...
drg Posted September 23, 2010 Share Posted September 23, 2010 I've had the same problem with both a IH and a Freightliner both had AD9 dryers. Always was fixed by changeing the filters in the dryers. While I was at it I usually put a pop of kit in at the same time. Quote Link to comment Share on other sites More sharing options...
alcoon61 Posted September 23, 2010 Author Share Posted September 23, 2010 Thanks for the replies and info. I will dig into it this weekend. Gonna go ahead and order a filter for the dryer. Quote Link to comment Share on other sites More sharing options...
alcoon61 Posted November 2, 2010 Author Share Posted November 2, 2010 Found cause. Pinhole in signal line near compressor. Plastic lines running unprotected and tie wrapped to the frame and had worn a flat spot on one side and eventually a hole. Another mack engineering booboo. 2 quick connects and a 6 inch piece of line to repair. Cost $11. Quote Link to comment Share on other sites More sharing options...
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